Best way to dig post holes for a deck?

I am planning on building a deck soon, and wanted opinions on the best way to dig post holes. I have to go down about 36" in clay with some rocks, the bottom of the hole needs to be 12" diameter, and I'll probably need 10 or 12 holes. Options I've been entertaining are:

1. Shovel and handheld clamshell type digger; free, but tiring.

2. One of those handheld gas-powered auger ones that you raise and lower yourself; about $40 for 3 hours from the local rental shop.

3. A Toro Dingo mini skid steer, which I think would be nearly effortless, but would cost about $200 to rent and I'm trying to keep costs to a minimum.

The deck I'm building is at my home so I'm not in too much of a hurry, but I don't want to spend too much time digging holes. Any advice wuold be appreciated.

While I'm at it, I'm leaning towards using screws to fasten the decking (2x6 treated). Some people say they like nails because they're faster, I think screws might be better in the long run??

(post #108300, reply #1 of 27)

Nails vs screws - I vote for screws - they are indeed slower and more expensive, but they don't pop up and "visit" your bare foot. 2nd choice would be SS annular ring shank nails - gun driven for speed.

Be careful as to fastener selection since you are using PT. Stainless or other PT rated coatings only.

(post #108300, reply #3 of 27)

i'd go with option #3 as well. Dug holes by hand (option #1) for our fence in compacted soil. Freeze depth here is also 36" (i stopped around 24"-30" because any further by that point was just tedious). Tried option #2 and it was worthless. The auger bit spun around like trying to put a screw through a tank tread.

Like you, i wasn't in any rush so i just finished by hand. But a lot of work. For $200, you could be done in a day, pour footings another day, then go at your own pace from there.

(post #108300, reply #6 of 27)

For 3 or 4 holes I'd use the clamshell, but only because I have a process that's fairly efficient. First, I use a long handled garden claw to break up the dirt/clay/rocks, as I'm using secondly, a heavy, compound-jawed clamshell digger that pulls up about 2x the amount a regular digger pulls up.

However, for as many holes as you're digging, I'd rent a gas powered auger if I have a helper and I don't want to destroy the lawn, or the mini-skidsteer if I'm working alone and don't care about the lawn.

Also, use stainless screws for the deck boards. Even screw-shank nails eventually work their way out.

(post #108300, reply #7 of 27)

Option 1 with the addition of a Bosch Demolition hammer with a clay spade. I have used a clamshell digger since 12 years old with moderate satisfaction. After getting Demolition hammer and a clay spade I feel ready to tackle anything my soil has to challenge me.

I find a big hammer with a clay spade is too much effort to move in and out of the hole.

I used to have an old makita that was too heavy but it only cost me a hundred dollars. Overall it worked ok. After it died I bought a new one that was worthless for digging as it was too heavy.

I bought it and it is awesome. It dug out 800 sq feet of basement six feet deep and aside from wearing out one clay spade it doesn't even seem to show any signs that the basement project even challenged it.

I always keep it handy if I need to dig post holes, trenches, etc.

If you don't need to own one it may not be cost effective to rent one compared to the dingo auger option 3.

(post #108300, reply #8 of 27)

We did roughly the same using a 2-man auger (with three men and a boy hanging onto it at many points). But for $200 I'd rent the skid-steer -- it wasn't an option when we did it. (Keep in mind that you're probably going to go over 3 hours on the 2-man.)

Use deck screws.

The modern conservative is engaged in one of man's oldest exercises in moral philosophy; that is, the search for a superior moral justification for selfishness. -John Kenneth Galbraith

Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed. --Herman Melville

(post #108300, reply #24 of 27)

I always get the strangest looks from people when I'm "caught" sharpening my digging tools or questioning the edge on their shovel.

I tell them that a shovel is a knife designed to cut dirt. Then the light seems to click on... ("But, won't it get dull again?") Most of my old oilstones live out in the shed now for touch-ups - the workshop is all waterstones or sandpaper.

But everyone still thinks I'm pulling their leg when I talk about sharpening screwdrivers...

(post #108300, reply #12 of 27)

Your profile doesn't say where you are located so this may not be an option. Google "Techno Metal Post". We use these a lot for decks, They come in and just screw the footing into the ground. When we submit plans for a permit we note that we are using them and the building inspector says to just call for a final, no footing inspection required.

(post #108300, reply #18 of 27)

They get about $165 per post here. Not quite as cheap as you could do it yourself, but a lot less then it's going to cost someone else to get me to dig a 1' x 4' hole, put a sonotube in it, fill it with concrete and stick a bolt and anchor plate on it.

(post #108300, reply #14 of 27)

If you go with the gas auger, practice by going to the local airport and grab a helicopter by the blades. Those augers will beat you up.

If you go with screws, get a cordless impact driver instead of a screw gun. Makes driving screws into PT a breeze. Also by a bunch of bits for the screws, they seem to chew them up. Also get ear plugs. The impact drivers are noisy enough to make it impossible to think.

I meditate, I burn candles, I drink green tea, and still I want to smack someone.

I meditate, I burn candles, I drink green tea, and still I want to smack someone.

(post #108300, reply #16 of 27)

Did you see where he says he's got 10-12 holes to drill, 12" diameter, 3 feet deep? That's not an easy afternoon with a bar and a clamshell. In the soil around here that would be 2-3 days of a guy stronger than I, working steady 8 hours/day.

The modern conservative is engaged in one of man's oldest exercises in moral philosophy; that is, the search for a superior moral justification for selfishness. -John Kenneth Galbraith

Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed. --Herman Melville